Polycarbonate (PC) and blends of polycarbonate with acrylonitrile, butadiene, and styrene terpolymer (PC/ABS) have found many uses in general, and specifically in medical devices, because polycarbonate combines a high level of heat resistance, transparency, good impact resistance, and it is easily molded. However, the prevalence of hospital acquired infections (HAI) requires medical devices to be exposed to a variety of commonly used cleaning liquids and polycarbonate, even blended with ABS, can suffer from a tendency to craze and crack under the effects of residual molded-in stresses, especially when contacted with such cleaning solutions. Polycarbonate which has crazed is, undesirably, more likely to experience brittle rather than ductile failure. This disadvantage has been somewhat relieved by the practice of blending polycarbonate with various substances such as the olefin polymers polyethylene, polypropylene, polyisobutylene, polyphenyleneoxide, or polyester as described for example in U.S. Pat. Nos. 3,431,224; 5,189,091; 5,262,476; 5,369,154; and 5,461,092. These added substances are capable of improving the resistance of polycarbonate to solvents, but they tend to cause an offsetting reduction in impact resistance and weldline strength of the blended composition. Additionally, it is frequently found that when the polycarbonate is modified with substances such as polyolefins, the added substances tend to separate in the blend from the polycarbonate and delaminate as evidenced by peeling or splintering. It would accordingly be desirable if substances admixed with polycarbonate for the purpose of improving the environmental stress crack resistance (ESCR) thereof (e.g. chemical resistance) did not also deleteriously affect its impact strength and weldline strength, and cause delamination as evidenced by peeling or splintering.